Electrical switching devices are well known in the field of medium and high voltage switching applications. They are e.g. used for interrupting a nominal current as well as currents originating from an electrical fault. For the purposes of this disclosure the term medium voltage refers to voltages from 1 kV to 72.5 kV and the term high voltage refers to voltages higher than 72.5 kV. The electrical switching devices, like said circuit breakers, may have to be able to carry high nominal currents of 3150 A to 6300 A and to switch very high short circuit currents of 31.5 kA to 80 kA at very high voltages of 72.5 kV to 1200 kV.
During interruption of a nominal or short circuit current within the electrical switching devices, the current commutates from the nominal contacts of the electrical switching device to its arcing contacts. They normally comprise as one arcing contact arcing contact fingers arranged around the longitudinal axis of the electrical switching device in a so-called arcing finger cage or tulip, and as a mating arcing contact a rod which is driven into the finger cage. However, there are also arrangements with two rods as arcing contacts, which are driven towards one another and are connected via their front faces during a closing operation.
During the opening or closing process of the electrical switching device an electric arc forms between the two arcing contacts. In order to interrupt the current, the electrical switching devices contain a dielectric fluid used as an insulating medium (e.g. SF6 gas) and for quenching the electric arc. Consequently, a part of the fluid located in the region where the electric arc is generated, called arcing volume, is considerably heated up (to around 20,000-30,000° C.) in a very short period of time. This part of the fluid builds up a pressure and is ejected from the arcing volume into so-called exhaust volumes. Particles are generated during operations of the circuit breaker (due to mechanical friction, erosion and ablation). These particles reduce the dielectric withstand capability if they approach highly dielectrically stressed locations.
US 2007/0068904 A1 discloses a high-voltage circuit breaker having an exhaust system with baffle walls arranged therein in an alternating manner to enforce a meandering path of the exhaust gases.
EP 2 120 244 A1 discloses a high-voltage circuit breaker having an exhaust system with a serial arrangement of pairs of baffle plates. Each pair of baffle plates provides a radial gap such that exhaust gas moving in longitudinal axial direction through the exhaust system is locally forced in the gap to follow a radial flow direction. Between subsequent pairs of baffle plates intermediate volumes are formed. Due to the radial flow directions in subsequent gaps, the exhaust gas follows a macro-swirling flow path in each intermediate volume, which results in improved cooling of the exhaust gases.
US 2014/0209568 A1 discloses a circuit breaker having an exhaust system with baffle plates arranged therein. The baffle plates have openings for transmitting exhaust gases. The openings of subsequent baffle plates are aligned in straight lines of sight with one another.
DE 10 2013 209 663 A1 discloses a circuit breaker having an exhaust system with an intermediate volume that provides a meandering path for the exhaust gases.
The prior art baffle wall arrangements improve cooling of the exhaust gases by creating turbulent flow conditions. The turbulent flow conditions cause particles entrained with the exhaust gases to be transported through the baffle wall arrangements.